I was cleaning out some old boxes from back in the day at KDWB with the #ClutterChallenge and I found this.
It's called The Chinese Birth Chart. Match up the age at which the mother conceived on the left with the month of conception on the right and you'll find the sex of the baby. It claims 99% accuracy and some people swear by it.
I blew it up a little on the bottom so it's easier to read.
So take a look. Was it accurate for you? Will it be accurate for your next baby?